Here is the circuit diagram of an ultrasonic mosquito repeller.The circuit is based on the theory that insects like mosquito can be repelled by using sound frequencies in the ultrasonic (above 20KHz) range.The circuit is nothing but a PLL IC CMOS 4047 wired as an oscillator working at 22KHz.A complementary symmetry amplifier consisting of four transistor is used to amplify the sound.The piezo buzzer converts the output of amplifier to ultrasonic sound that can be heard by the insects.

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Comments

Satya Brata Dutta

August 16, 2016

I think easy to test the circuit whether functioning or not is possible easily. Take multi meter on 10 volt AC range with series a capacitor of .01 mfd disc type and measure on the point where pizzo point connected . If the meter deflect then it is functuionin.

Hello, Im an norwegian engineer-student, and I am having your circuit as a project, both making and attempting to explain it. Making it wont be that much of a problem, but understanding it is a little more tricky. I wondered if you could explain a little bit how/why you have used 4 transistors, for example, and why this circuit will work the way it does.

It would mean a lot to me!

And, could you answer me by mail by some chance?
On beforehand, thank you.

Hi This is called bridged push pull output. This circuit will provide 4 times the normal 2 transistor push pull output connecting through a coupling capacitor. IC 4047 is an oscillator whose frequency is set by R1 & C1. The complimentary output of the IC which is available on pin no 10 & 11 are fed to the bridged output circuit. Since the frequency used for repelling mosquitoes is in the ultrasonic range a piezo transducer, which respond to Ultrasonic sound better is used for producing sound, instead of standard loud speaker.

Hi dear sir
The circuit it so good but
I replaced the piezo buzzer to tweeter transducer 8 ohm
Is this will work or not
Other thing when I tested the circuit the Q1 and Q4 were so hot
Is this normal or I have problems in circuit

We’re a group of volunteers and opening a brand new plan in our little local community. Your website offered us with beneficial info to work on. You have done a striking position and our complete community shall be thankful to you.

Hi Susan connect 4.7nF in parallel to C1 the oscillator frequency will be in audible range. now check any out put is there if not check all the components and IC pin connections. if it gives audible sound, remove the capacitor connected in parallel, the circuit is ready for use. Piezotransducer will emit the in audible signal of the oscillator. sound level indicator is an equipment to measure the sound level (noise level) in an environment. they operate in human audible range only.

If you use R1 as 22K and C1 as 10PF tha frequency out will be 1000kHz, similarly for 10 kHz C1 should be 100pF and R1 should be 220k or 22k and 1000pF. for 20kHz either you make C1 half (500pF) the value or R1 (11k)half the value(as the formula is inversely proportional)

C2 is an electrolytic capacitor and they are available in different voltage ratings, from few volts to hundreds of volts and thats why its a common practice to represent the voltage rating of electrolytic capacitors in the circuit diagram.

C1 is a ceramic capacitor and the commonly available ones are rated from 50V to 400V. Some manufacturers represent the voltage rating using some code while others not. Any way we can guess that a commonly available ceramic disc capacitor will be rated at least 50V or so.

Here the working voltage is 12V and a 50V ceramic capacitor will be more than enough.

Hi Zaman these small speakers may not respond beyond 11 to 12kHz. only hi-fi tweeters can respond they will be quite expensive. Hence Piezo tweeters are quite in expensive. this is normally used as additional attachment with car system speakers or part of portable sound system. you can use them.

Dear sir,
I am a chemical engr by profession. I need an electronic mosquito repellent which may be powered by 9 volt battery, for my personal use in travelling.
I assembled mosquito repellent circuit. I am observing, mosquitoes are not affected by this. I don’t know whether the circuit is working or not. I used a piezo tweeter which works with 8000+ frequencies which I can hear (in other tests). I want to know where to be connected with No 2 leg of IC 4047. Can you please suggest me in this regard?
If it works, I want to assemble few more for our use. Can you suggest me how to make a mosquito repellent with Variable Frequency (from 16 kHz to 45 kHz+) with sufficiently powerful output so that it should be sufficient to a 30 X 40 house. Or can you prepare me one such piece?
regards
Vishwanath

There are also insect repellent products available based on sound production, particularly ultrasound (inaudibly high frequency sounds). These electronic devices have been shown to have no effect as a mosquito repellent by studies done by the EPA and many universities.

Thanks alot for the cct! But my question instead of ic,can one use multivibrator circuit to generate the frequency! Since T(time const)=RC and we know that F(freqency)=1/T.We just make capacitor const and increase our resistor value to generate 20khz and above.Then connect output of our NPN collector with ultrasonic transmitter! Can it work that way?

Hi Seetharaman,
Thanks for reply. Can u do me another favour by telling the number of resisters used and the specifications of resistors.If there is any diode used please tell me the numbers and specs.
thanks.

Hi Fahad the number of transistors are 4 and IC is one. The transistor are SK100 PNP general purpose transistor. SL100 NPN general purpose transistor. you can use the recent types 8050 for SL100 and 8550 for SK100.

Hi Badeekh you cannot use piezo buzzer they have built in electronics for producing music or sound. piezo transducer or piezo tweeter. you can use ultrasonuc transmitter (sender transducer), ensure that they are capable of reproducing from 20kHz.

Hi Hider since the frequency generated is beyond our hearing it will be difficult to hear, but you can make a sound level indicator using a condencer mic with suitable electronics.
Piezo transducers can respond from around 1kHz to beyond audible range. they are normally used as tweeters in hifi loud speaker systems.
Car reverse horns musical chime electronic music generators use them as they are wheather proof and they contain no moving parts like magnetic voice coil loud speakershttp://www3.telus.net/chemelec/Projects/SPL/SPL-1.png

thanks for the circuit… but i want to know how the ic cd4047 works in this circuit(does if change the electric signal to sound signal)…and does variable resistance change the output frequency..
plz reply me.. as soon as possible….

Hi Senthil the ultasonic frequency range is just beyond human hearing range of 20KHz to 100KHz. There transducers available for sender and receiver. you can use them with amplification and detection and convert into signal strength with a DMM in Volt/mV range.

Hi Prakash you can use 16 ohms tweeter or two 8 ohms tweeters in series.
Hi Firoz assemble this try using it near the group of mosquitos, you can see the reaction of them. you also see my aug 30th comment

Sir,
vanakkam,
i happened to see your article in the site. i am 60 now. about more than 20 years back i was testing such articles as a hobby. now due to over age and due eye problems i am unable to do any work.

will you kindly assemble one and send me for my household use, because we are suffering from heavy invasion of mosquitoes at our city. further the use of chemical repellents make my asthma problems more aggravated and throw me to admission to hospitals for emergency attention.

i am ready to send the cost in advance if you can kindly mail me the details. rather if it is at market it may please be informed.

thank you very much for your publication.
i further wish you to develop many projects which are needed for the people’s welfare and publish such in the website.

pls i urgently need a workable simplified circuit diagram for mosquito repellant without any ic. please forward it to my mail cashwot@yahoo.com. I will appreciate it better it many different circuit can be forwarded. Thank

Hi Vignesh This circuit is based on the simple principle that insects gets immobilised or driven away by using ultrasonic sound above 20KHz. The above circuit operates around 22KHz. You can try by assembling and try to direct it towards the group of mosquitos, you can see the results for yourself. K1 should be Phiezo tweeter (used in two in ones for hi frequency reproduction).

Hi Sonny you can try to assemble a variable frequecy oscillator in the range of 16 to 20KHz with a suitable amplifier and a HF transducer(ceramic tweeters. This range will affect only mosquitos not other living things. You can find out at what frequecny the mosquitos flie away as your sounder approaches them.

Is this mosquito repeller can be use in our piggery? we noticed our pigs had several bites from mosquitos.
Since this circuit is operated in sound frequency above 20khz range, would there be any side effects in our pigs?